The proposed research represents an integrated chemical and physicochemical approach to elucidate the molecular parameters involved in the association of calmodulin with Beta-endorphin, phenothiazines, phosphodiesterase, calcium and vanadyl. Direct binding studies of endorphin and phenothiazines will be conducted to pursue the nature of the cooperativity that has been observed. Chemical studies will focus on differential trace labeling to assess individual lysine reactivities in calmodulin as influenced by the various ligands. A feasibility study will be undertaken using a novel technique for identification of the endorphin binding sites on calmodulin and the regions. Considerable effort will be devoted to ESR spectroscopy of spin labeled calmodulin and vanadyl-calmodulin complexes, several probes will be used to modify calmodulin, and spin labeled chlorpromazine-calmodulin complexes will be investigated. These studies should provide useful information on the mechanisms by which calmodulin can associate with a variety of simple ligands and complex enzymes.